Systems of application to ensure the electric feed defined in three basic levels according to the needs to be covered are conventionally known:
1. Total break and subsequent restoration in less than 30 seconds.
2. Short break or even no break but with a big deterioration of the values of the frequency and/or voltage during at least some cycles&gt;to 20 milliseconds.
3. No break nor deterioration in the variables of frequency and/or voltage in .+-.1% the former and +10-8% the latter for a time less than 50 milliseconds (two and a half cycles at 50 Hz.)
The first one of them is usually solved by means of installing an emergency generating set with automatic operation, which starts up by itself in view of an absence of the public network, driving the corresponding Line-Set transfer equipment once the motor is ready to distribute its power. This entire operation must not exceed 30 seconds, and the normal thing in sets with preheating and prelubrication tends to be from 4 to 10 seconds.
The second one is a bit more complex and motor-generator-inertia wheel set, which is coupled to a diesel engine by means of an electromagnetic clutch, is used for this purpose. In normal operation the motor generator set acts as a frequency converter 50 Hz/50 Hz, (or others), the permanent power load being connected to its secondary (the generator.) The inertia wheel is kept permanently coupled to the same.
In view of an absence of the public network, the order for the start of the diesel engine is immediately produced and the engine is in the position to supply power 4 or 5 seconds after the order has been given.
During this interval of time, the inertia wheel yields part of the energy accumulated in it (1/2 Iw2), which is made possible by means of the corresponding reduction of its angular speed, and therefore of the frequency of the current supplied to the power load. Depending on the size of the wheel more or less effective short-break sets can be obtained. The first ones are prohibitive due to the high degree of mechanical complexity that the handling of large wheels requires (keep in mine that the wheel must be made by forging, therefore the dimensions thereof are limited by the availability of the existing forging means) and because the high mechanical reactions make it necessary to extraordinarily reinforce the bearings.
The no-break system has only been solved up to the present by means of the use of electric accumulators. At the present time there are two methods for solving the problem: the rotary and the static ones.
The rotary one was the one initially used until 1975, as of when it has been virtually replaced by the static system up to the present. It should be pointed out that nowadays there is a certain tendency of greater confidence in the rotary systems in the most industrialized countries basically due to reasons of reliability.
The rotary system uses a controlled rectifier in order to keep the battery charged and simultaneously to provide the necessary energy to a motor-generator set.
In normal operation the energy of the public network is rectified and directed in a controlled manner to a continuous current motor to shoe shaft a three-phase alternator, which directly feeds at the "critical load", is coupled.
Is the absence of the network, the continuous current motor takes energy from the batteries keeping the rotation speed of the unit unvaried for the period of time that the size of the accumulator battery allows (normally 10 to 20 minutes.)
The static system replaces the motor-generator set of the rotary system by a three-phase (or one-phase) inverter by means of the adequate use of semiconducting power elements, either thyristors or else transistors which generate an alternating voltage whose main variables: frequency, voltage and harmonic content, have static and dynamic values which are acceptable for most of the "critical power loads."
Both systems suffer from the effect of having an autonomy limited by the size of the battery, therefore, they require the simultaneous aid of an emergency generator (normally diesel) to limit their autonomy.
The first one, although it is more reliable than the second one, requires more and more burdensome maintenance.
The problem of installations is big for both, since the battery requires certain care for its installation.
From the analysis of the foregoing paragraphs the non-existence on the market up to the present of any continuity system with limited autonomy which can be considered as a sole element or device is inferred. This is precisely the object of the present invention.